U.S. patent number 7,227,153 [Application Number 11/002,648] was granted by the patent office on 2007-06-05 for method for measuring ultraviolet radiation and ultraviolet measuring device.
This patent grant is currently assigned to Fuji Xerox Co., Ltd.. Invention is credited to Shigeru Yagi.
United States Patent |
7,227,153 |
Yagi |
June 5, 2007 |
Method for measuring ultraviolet radiation and ultraviolet
measuring device
Abstract
An ultraviolet measuring method using an ultraviolet sensitive
element, comprising: measuring an ultraviolet intensity with the
ultraviolet sensitive element at a sun altitude; and determining an
integrated ultraviolet intensity within a specific ultraviolet
wavelength range or a response index by converting the measured
intensity to the integrated ultraviolet intensity within the
specific ultraviolet range or the response index by using a
conversion factor corresponding to the sun altitude, wherein the
conversion factor is a function of at least sun altitude. An
ultraviolet measuring method, using an ultraviolet sensitive
element with spectral sensitivity to a specific wavelength range,
comprising: measuring an ultraviolet intensity with the ultraviolet
sensitive element; and correcting the measured ultraviolet
intensity according to sun altitude information for an arbitrary
point in time so as to predict an ultraviolet intensity at the
point in time.
Inventors: |
Yagi; Shigeru (Kanagawa,
JP) |
Assignee: |
Fuji Xerox Co., Ltd. (Tokyo,
JP)
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Family
ID: |
34932037 |
Appl.
No.: |
11/002,648 |
Filed: |
December 3, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050236576 A1 |
Oct 27, 2005 |
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Foreign Application Priority Data
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Apr 23, 2004 [JP] |
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2004-128702 |
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Current U.S.
Class: |
250/372;
250/472.1 |
Current CPC
Class: |
G01J
1/429 (20130101) |
Current International
Class: |
G01J
1/00 (20060101) |
Field of
Search: |
;250/472.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 120 636 |
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Aug 2001 |
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EP |
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1 120 636 |
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Sep 2003 |
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EP |
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A-11-264760 |
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Sep 1999 |
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JP |
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WO 97/43608 |
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Nov 1997 |
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WO |
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WO 03/031921 |
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Apr 2003 |
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WO |
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Other References
"Forecast of Surface Ultraviolet Radiation," 1995-2006 Tsinghua
Tongfang Oprical Disc Co., Ltd., pp. 28-42, Chinese text and
partial translation. cited by other.
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Primary Examiner: Porta; David
Assistant Examiner: Malevic; Djura
Attorney, Agent or Firm: Morgan, Lewis & Bockius,
LLP
Claims
What is claimed is:
1. An ultraviolet measuring method using an ultraviolet sensitive
element, comprising: measuring an ultraviolet intensity within a
first ultraviolet wavelength range with the ultraviolet sensitive
element at a sun altitude; and determining an integrated
ultraviolet intensity within a second ultraviolet wavelength range
by converting the measured intensity to the integrated ultraviolet
intensity within the second ultraviolet wavelength range by using a
conversion factor corresponding to the sun altitude, wherein the
conversion factor is a function of at least sun altitude.
2. The ultraviolet measuring method using an ultraviolet sensitive
element according to claim 1, wherein the second ultraviolet
wavelength range is substantially within the first ultraviolet
wavelength range.
3. The ultraviolet measuring method using an ultraviolet sensitive
element according to claim 1, wherein the second ultraviolet
wavelength range is substantially outside of the first ultraviolet
wavelength range.
4. An ultraviolet measuring method using an ultraviolet sensitive
element, comprising: measuring an ultraviolet intensity within a
first ultraviolet wavelength range with the ultraviolet sensitive
element at a sun altitude; and determining a response index within
a second ultraviolet range by converting the measured intensity to
the response index by using a conversion factor corresponding to
the sun altitude, wherein the conversion factor is a function of at
least sun altitude.
5. The ultraviolet measuring method using an ultraviolet sensitive
element according to claim 4, wherein the second ultraviolet
wavelength range is substantially within the first ultraviolet
wavelength range.
6. The ultraviolet measuring method using an ultraviolet sensitive
element according to claim 4, wherein the second ultraviolet
wavelength range is substantially outside of the first ultraviolet
wavelength range.
7. An ultraviolet measuring method using an ultraviolet sensitive
element having spectral sensitivity in a first ultraviolet
wavelength range, comprising: measuring an integrated ultraviolet
intensity within the first ultraviolet wavelength range with the
ultraviolet sensitive element at a sun altitude; and (1)
determining an integrated ultraviolet intensity within a second
ultraviolet wavelength range by correcting the measured intensity
on the basis of a standard intensity ratio and a sun altitude
correction factor for the standard intensity ratio wherein the
standard intensity ratio is a ratio between an integrated
ultraviolet intensity within the second ultraviolet wavelength
range and an integrated ultraviolet intensity within the first
ultraviolet wavelength range, with respect to a standard solar
radiation spectrum, or (2) determining a response index on the
basis of the measured intensity, a standard intensity ratio, and a
sun altitude correction factor for the standard intensity ratio
wherein the standard intensity ratio is a ratio between a response
index and an integrated ultraviolet intensity within the first
ultraviolet wavelength range, with respect to a standard solar
radiation spectrum.
8. The ultraviolet measuring method according to claim 7, wherein
the sun altitude correction factor for the standard intensity ratio
is determined on the basis of at least a light path length of
sunlight in the earth's atmosphere.
9. The ultraviolet measuring method according to claim 7, wherein
the sun altitude correction factor for the standard intensity ratio
is determined on the basis of at least ozone concentration
information.
10. The ultraviolet measuring method according to claim 7, wherein
the response index is an index determined by using an erythema
curve.
11. An ultraviolet measuring method according to claim 7, further
comprising correcting the measured ultraviolet intensity according
to sun altitude information for an arbitrary point in time so as to
predict an ultraviolet intensity at the point in time.
12. The ultraviolet measuring method according to claim 11, further
comprising integrating the predicted ultraviolet intensity over a
specified time period to predict an integrated ultraviolet
intensity.
13. An ultraviolet measuring method according to claim 12, wherein
a kind of ultraviolet ray protective agent is decided on the basis
of the predicted integrated ultraviolet intensity.
14. An ultraviolet measuring device comprising an ultraviolet
sensitive element and a conversion device, wherein the conversion
device converts a value measured by the ultraviolet sensitive
element within a first ultraviolet wavelength range at a sun
altitude to an integrated ultraviolet intensity within a second
ultraviolet wavelength range by using information of the sun
altitude.
15. The ultraviolet measuring method using an ultraviolet sensitive
element according to claim 14, wherein the second ultraviolet
wavelength range is substantially within the first ultraviolet
wavelength range.
16. The ultraviolet measuring method using an ultraviolet sensitive
element according to claim 14, wherein the second ultraviolet
wavelength range is substantially outside of the first ultraviolet
wavelength range.
17. An ultraviolet measuring device comprising an ultraviolet
sensitive element and a conversion device, wherein the conversion
device converts a value measured by the ultraviolet sensitive
element within a first ultraviolet wavelength range at a sun
altitude to a response index within a second ultraviolet wavelength
range by using information of the sun altitude.
18. The ultraviolet measuring method using an ultraviolet sensitive
element according to claim 17, wherein the second ultraviolet
wavelength range is substantially within the first ultraviolet
wavelength range.
19. An ultraviolet measuring device comprising: an ultraviolet
sensitive element with spectral sensitivity to a first wavelength
range; a storage unit which stores a standard intensity ratio; and
a correction unit which corrects an intensity measured by the
ultraviolet sensitive element on the basis of the standard
intensity ratio and a sun altitude correction factor to obtain an
integrated ultraviolet intensity within a second ultraviolet
wavelength range or to obtain a response index, wherein the
standard intensity ratio is a ratio between an integrated
ultraviolet intensity within the second ultraviolet wavelength
range or a response index and an integrated ultraviolet intensity
within the first ultraviolet wavelength range, with respect to a
standard solar radiation spectrum.
20. The ultraviolet measuring device according to of claim 19
further comprising: a sun altitude information acquisition unit
which acquires sun altitude information to be used for determining
the sun altitude correction factor for the standard intensity
ratio.
21. The ultraviolet measuring device according to claim 20, wherein
latitude information or longitude information, and date and time
information are acquired as the sun altitude information.
22. The ultraviolet measuring device according to claim 20, wherein
latitude information, longitude information, and date and time
information are acquired as the sun altitude information.
23. The ultraviolet measuring device according to claim 19, wherein
the response index is an index determined by using an erythema
curve.
24. An ultraviolet measuring device according to claim 19, wherein
the storage unit further stores sun altitude information for
arbitrary points in time; and the correction unit further corrects
the intensity measured by the ultraviolet sensitive element
according to sun altitude information for an arbitrary point in
time so as to predict an ultraviolet intensity at the point in
time.
25. The ultraviolet measuring device according to claim 24, further
comprising a calculation unit which calculates an integrated
ultraviolet intensity over a specified period.
26. The ultraviolet measuring device according to claim 25, further
comprising a decision unit which decides the kind of ultraviolet
ray protective agent on the basis of the predicted integrated
ultraviolet intensity.
Description
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority under 35 USC 119 from Japanese
patent Application No. 2004-128702, the disclosure of which is
incorporated by reference herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ultraviolet measuring method
and an ultraviolet measuring device, which can easily measure
ultraviolet rays in living environment and can get information on
specific ultraviolet rays such as an amount of ultraviolet rays
which have direct influences on human bodies.
2. Description of the Related Art
One of the biggest problems concerning the global environment has
been an increase in the amount of ultraviolet radiation on the
surface of the earth caused by destruction of ozone layer. Such
ultraviolet rays cause health problems such as development of skin
cancers, development of light-hypersensitivity, and light aging.
Moreover, ultraviolet rays cause aesthetic problems such as
pigmented spots and freckles.
Therefore, measurement of ultraviolet rays in our living
environment has become more important from the viewpoint of beauty
and health care.
However, a dedicated ultraviolet gauging device is required for
measurement of an amount of ultraviolet rays. Since it is a bother
to carry a dedicated UV (ultraviolet) measuring device, it has been
not easy to measure ultraviolet rays.
The ultraviolet rays have various kinds of influences on living
bodies. Accordingly, there are various ways of expressing an amount
of ultraviolet rays, depending on the purpose for the measurement
of ultraviolet rays. For example, an amount of ultraviolet rays may
be represented by the total amount of ultraviolet rays (290 to 400
nm), by the amount of ultraviolet rays measured by an ultraviolet
sensor having sensitivity only to the UVA range (320 to 400 nm), or
by the amount of ultraviolet rays measured by an ultraviolet sensor
having sensitivity only to the UVB range (290 to 320 nm).
SUMMARY OF THE INVENTION
However, the ultraviolet ray sensors do not have characteristic
curves corresponding to, for example, an erythema curve determined
by the capability of developing skin sunburn. The sensors are
calibrated at representative wavelengths within their spectral
sensitivity curve; therefore, the sensors do not have similar
sensitivity distributions to delta functions within the defined
wavelength range.
The index determined by the erythema curve is called "the UV
index." The UV index represents the energy amount of ultraviolet
rays per one hour around noon weighted by the erythema curve.
Generally, the UV indexes are classified into over ten grades, but
are also classified into five levels expressed by phrases
corresponding to human feeling.
The UV index is obtained by weighting each wavelength in the UVA
and UVB ranges by a corresponding value on the erythema curve.
Accordingly, an accurate value has been obtained only from the
spectral irradiance. In order to measure the spectral irradiance,
it is necessary to use a large-sized measuring device, thus the
measurement is not convenient. Further, an amount of the UVA cannot
be measured by a spectral sensitivity measuring device adapted to
such a measurement of ultraviolet rays which are capable of causing
erythema. Therefore, ultraviolet rays through a window, which has
large influences on aesthetic problems such as pigmented spots and
freckles, can not be taken into consideration.
As described above, there has been no method for getting specific
ultraviolet information easily, and an improved method has been
required.
The present invention has been made, considering the
above-described problems of conventional methods.
The ultraviolet measuring methods of the present invention utilize
a fact that an wavelength distribution of intensity of ultraviolet
light on the surface of the earth is strongly affected by
absorption and scattering in the stratosphere, but is not
significantly affected by the weather or the altitude of the
observation point. Accordingly, the wavelength distribution of
intensity of ultraviolet light on the surface of the earth is
mainly affected by the sun altitude. Although the intensity of
ultraviolet light on the surface of the earth is affected by the
weather or the like, the wavelength distribution can be estimated
if information on the sun altitude is obtained. This principle can
be applied to calculate an entire intensity (In2) of ultraviolet
light within a specific wavelength range, as described in the
following.
Each ultraviolet sensitive element has a specific characteristic in
terms of sensitivity. Here, an ultraviolet intensity actually
measured by the ultraviolet sensitive element is represented by
"Ma." If the sun altitude is the same, the ratio (Ra1) of "In2" to
"Ma" is almost the same since the wavelength distribution is almost
the same. If a conversion table is once made on which "Ra1" values
for respective sun altitude are written, it is possible to obtain
the value "Ma" by the ultraviolet sensitive element and to
calculate "In2" from "Ma" by multiplying "Ma" by the conversion
factor for the sun altitude on the conversion table. The sun
altitude can be calculated or measured or inputted. The conversion
table may be stored in a memory. However, the conversion table is
not essential since the conversion factor can be calculated at the
observation point.
The same technique can be applied to calculate an index (a response
index) which is related to a specific influence on human body or
the like. The UV index is an example of such an index. The response
index (Ri) is obtained by multiplying an intensity at a wavelength
by a corresponding value on a response curve and integrating the
product along the wavelength axis. If the sun altitude is the same,
the ratio (Ra2) of "Ri" to "Ma" is almost the same since the
wavelength distribution is almost the same. If a conversion table
is once made on which "Ra2" values for respective sun altitude are
written, it is possible to obtain the value "Ma" by the ultraviolet
sensitive element, to measure the sun altitude, and to calculate
"Ri" from "Ma" by multiplying "Ma" by the conversion factor for the
sun altitude on the conversion table. The sun altitude can be
calculated or measured or inputted. The conversion table may be
stored in a memory. However, the conversion table is not essential
since the conversion factor can be calculated at the observation
point.
In these techniques, it is not necessary for the conversion table
to include conversion factors for every sun altitude. The
techniques can be applied if the conversion table includes
conversion factors for some practical sun altitudes. The conversion
factors may be determined experimentally or theoretically or by a
combination of experiment and theory.
The ultraviolet sensitive element has not necessarily been
calibrated to an integrated ultraviolet intensity within a specific
wavelength range. However, when the ultraviolet intensity is
changed while the wavelength distribution is fixed, the ultraviolet
sensitive element has to accurately indicate the ratio of the
intensity change. For example, if the ultraviolet intensity is
doubled while the wavelength distribution is fixed, the intensity
indicated by the ultraviolet sensitive element has to be doubled.
Since the UVA occupies most of the solar ultraviolet rays, it is
practically sufficient that the measured intensity has been so
calibrated that the measured intensity corresponds to UVA
intensity. This calibration may be conducted within the measuring
device, or there may be provided a calibration table or the like so
that the calibration is conducted outside of the measuring
device.
A first aspect of the present invention is to provide an
ultraviolet measuring method using an ultraviolet sensitive
element, comprising:
measuring an ultraviolet intensity with the ultraviolet sensitive
element at a sun altitude; and
determining an integrated ultraviolet intensity within a specific
ultraviolet wavelength range by converting the measured intensity
to the integrated ultraviolet intensity within the specific
ultraviolet range by using a conversion factor corresponding to the
sun altitude,
wherein the conversion factor is a function of at least sun
altitude.
A function "F (.theta.)=C" is excluded from the scope of the
function, wherein .theta. represents the sun altitude and C
represents a constant.
The conversion factor may correspond to a ratio of an integrated
ultraviolet intensity within the specific ultraviolet range at the
sun altitude to an intensity measured by the ultraviolet sensitive
element at the sun altitude.
A second aspect of the present invention is to provide an
ultraviolet measuring method using an ultraviolet sensitive
element, comprising:
measuring an ultraviolet intensity with the ultraviolet sensitive
element at a sun altitude; and
determining a response index by converting the measured intensity
to the response index by using a conversion factor corresponding to
the sun altitude,
wherein the conversion factor is a function of at least sun
altitude.
A function "F (.theta.)=C" is excluded from the scope of the
function, wherein .theta. represents the sun altitude and C
represents a constant.
The conversion factor may correspond to a ratio of a response index
at the sun altitude to an intensity measured by the ultraviolet
sensitive element at the sun altitude.
Each of the conversion factors can be considered as a product of
two factors. One of the factors may be a factor which converts the
measured intensity to a desired integrated intensity or a desired
response index at a predetermined sun altitude. The other factor
may be a factor which reflects the difference in wavelength
distribution between a sun altitude and the predetermined sun
altitude. The intensity indicated by the ultraviolet sensitive
element can be calibrated so that the indicated intensity
corresponds to an integrated ultraviolet intensity within a
specific wavelength range. In the following aspects, the standard
intensity ratio corresponds to the first factor and the sun
altitude correction factor corresponds to the second factor.
A third aspect of the present invention is to provide an
ultraviolet measuring method using an ultraviolet sensitive element
having spectral sensitivity in a first ultraviolet wavelength
range, comprising:
measuring an integrated ultraviolet intensity within the first
ultraviolet wavelength range with the ultraviolet sensitive element
at a sun altitude; and
determining an integrated ultraviolet intensity within a second
ultraviolet wavelength range by correcting the measured intensity
on the basis of a standard intensity ratio and a sun altitude
correction factor,
wherein the standard intensity ratio is a ratio between an
integrated ultraviolet intensity within the second ultraviolet
wavelength range and an integrated ultraviolet intensity within the
first ultraviolet wavelength range, with respect to a standard
solar radiation spectrum.
The standard intensity ratio and the sun altitude correction factor
each may have been obtained before the observation or may be
calculated on the observation point.
A fourth aspect of the invention is to provide an ultraviolet
measuring method using an ultraviolet sensitive element having
spectral sensitivity in a first ultraviolet wavelength range,
comprising:
measuring an integrated ultraviolet intensity within the first
ultraviolet wavelength range with the ultraviolet sensitive element
at a sun altitude; and
determining a response index on the basis of the measured
intensity, a standard intensity ratio, and a sun altitude
correction factor,
wherein the standard intensity ratio is a ratio between a response
index and an integrated ultraviolet intensity within the first
ultraviolet wavelength range, with respect to a standard solar
radiation spectrum.
The standard intensity ratio and the sun altitude correction factor
each may have been obtained before the observation or may be
calculated on the observation point.
The response index with respect to the standard solar radiation
spectrum may be determined from the standard solar radiation
spectrum and a response curve. Specifically, the response index
with respect to the standard solar radiation spectrum may be
determined by integrating (intensity at a
wavelength.times.corresponding value on a response curve) along the
wavelength axis.
In the third and fourth aspects, a value measured by an ultraviolet
sensitive element is multiplied by the standard intensity ratio and
the sun altitude correction factor, thus corrected. The standard
intensity ratio is obtained by dividing an integrated ultraviolet
intensity of the standard solar radiation spectrum within a
specific wavelength range by an integrated ultraviolet intensity of
the standard solar radiation spectrum within the first ultraviolet
wavelength range, wherein the standard solar radiation spectrum was
measured separately. In the present invention, the integrated
ultraviolet intensity of the standard solar radiation spectrum
within a specific wavelength range refers to an integrated
ultraviolet intensity of the standard solar radiation spectrum
within the second ultraviolet wavelength range or a response index
of the standard solar radiation spectrum determined by the standard
solar radiation spectrum and by a specific response curve.
The third and fourth aspects can be modified to as follows:
An ultraviolet measuring method using an ultraviolet sensitive
element with spectral sensitivity to a specific range,
comprising:
correcting an actually measured value of solar ultraviolet
intensity which is measured with the ultraviolet sensitive element
on the basis of a standard intensity ratio and a sun altitude
correction factor for the standard intensity ratio, to obtain an
ultraviolet intensity within a second ultraviolet wavelength range
or ultraviolet intensity related to a specific response curve,
wherein the standard intensity ratio is a ratio between a first
integrated ultraviolet intensity of a standard spectroscopic solar
radiation spectrum within a first ultraviolet wavelength range and
a second integrated ultraviolet intensity of the standard
spectroscopic solar radiation spectrum within a second ultraviolet
wavelength range or a third integrated ultraviolet intensity of the
standard spectroscopic solar radiation spectrum obtained from the
standard spectroscopic solar radiation and a specific response
curve.
The ultraviolet intensity related to a specific response curve and
the third integrated ultraviolet intensity may be considered as a
response index.
According to the third and fourth aspects of the invention, with a
simple constitution, it is possible to easily obtain specific
ultraviolet information (ultraviolet intensity within a second
ultraviolet wavelength range, or ultraviolet intensity related to a
specific response curve) from actually measured values, regardless
of the weather. It is also possible to determine the total amount
of ultraviolet rays. Moreover, for example, ultraviolet intensities
and amounts of ultraviolet rays of UVA and UVB can be determined
separately from each other.
However, in order to obtain an absolute value of ultraviolet
intensity and an amount of the ultraviolet rays, an actually
measured value obtained by an ultraviolet sensitive element has to
be calibrated so that the measured value indicates the ultraviolet
irradiance within the defined wavelength range of the element. The
calibration may be conducted by using a standard light source or
the like.
Examples of the first ultraviolet wavelength range include the
whole ultraviolet ray range (for example, a wavelength range of
UVA+UVB, that is, 290 to 400 nm), a wavelength range of UVB (290 to
320 nm) or a wavelength range of UVA (320 to 400 nm).
The second ultraviolet wavelength range may be within the first
ultraviolet wavelength range. For example, when the first
ultraviolet wavelength range is the whole ultraviolet ray range of
290 to 400 nm, the second ultraviolet wavelength range may be the
UVB wavelength range of 290 to 320 nm.
An example of the response curve is the erythema curve. When the
erythema curve is applied and the first ultraviolet wavelength
range is, for example, the whole ultraviolet range of 290 nm to 400
nm, the response index calculated from the solar spectrum and the
specific response curve may be an erythema ultraviolet intensity
within 290 to 400 nm. Furthermore, for example, when the first
ultraviolet wavelength range is UVB of 290 to 320 nm, the response
index may be an erythema ultraviolet intensity within 290 to 320
nm.
Thereby, an ultraviolet intensity which directly affects human body
(or an UV index corresponding to the intensity) can be obtained. An
arbitrary response curve which represents the influence of
ultraviolet rays may be used as the response curve. For, example,
the response curve may be a response curve of the influence on
DNA.
The wavelength range of the spectral sensitivity of an ultraviolet
sensitive element may or may not include the whole first
ultraviolet wavelength range and the whole second ultraviolet
wavelength range. For example, when the spectral sensitivity range
of an ultraviolet sensitive element is 290 to 400 nm, the
ultraviolet intensity of UVB of 290 to 320 nm can be obtained as
the second ultraviolet wavelength range. When the spectral
sensitivity range of an ultraviolet sensitive element is 320 to 400
nm, the ultraviolet intensity within the wavelength range of UVB of
290 to 320 nm, which is out of the spectral sensitivity range, may
be determined as the second ultraviolet wavelength range. However,
in this case, values actually measured by the ultraviolet sensitive
element must have been corrected to ultraviolet intensity of UVB
which occupies most of the solar ultraviolet radiation.
Preferably, the sun altitude correction factor for the
above-described standard intensity ratio may be determined on the
basis of the light path length of the sunlight within the earth's
atmosphere. Furthermore, it is preferable to consider ozone
concentration information in determining the sun altitude
correction factor.
The sun altitude varies depending on the latitude and/or the
longitude, and date and time. The attenuation amount of the
sunlight upon transmission through the stratosphere and the
troposphere varies depending on the light path length within the
stratosphere and the troposphere. In addition, the transmission
coefficient varies depending on the wavelength. Moreover, the
attenuation amount upon transmission through the ozone layer varies
depending on the light path length within the ozone layer and the
ozone concentration of the ozone layer, in the case of UVB
wavelength range or of an ultraviolet wavelength range related to
the erythema curve. Accordingly, an accurate sun altitude
correction factor can be obtained on the basis of the light path
length of the sunlight within the earth atmosphere and ozone
concentration information.
A fifth aspect of the invention is to provide an ultraviolet
measuring device comprising an ultraviolet sensitive element and a
conversion device, wherein the conversion device converts a value
measured by the ultraviolet sensitive element at a sun altitude to
an integrated ultraviolet intensity within a specific wavelength
range by using information of the sun altitude.
A sixth aspect of the invention is to provide an ultraviolet
measuring device comprising an ultraviolet sensitive element and a
conversion device, wherein the conversion device converts a value
measured by the ultraviolet sensitive element at a sun altitude to
a response index by using information of the sun altitude.
The details of the conversion may be the same as in the description
of the ultraviolet measuring methods.
A seventh aspect of the invention is to provide an ultraviolet
measuring device comprising:
an ultraviolet sensitive element with spectral sensitivity to a
first wavelength range;
a storage unit which stores a standard intensity ratio; and
a correction unit which corrects an intensity measured by the
ultraviolet sensitive element on the basis of the standard
intensity ratio and a sun altitude correction factor to obtain an
integrated ultraviolet intensity within a second ultraviolet
wavelength range,
wherein the standard intensity ratio is a ratio between an
integrated ultraviolet intensity within the second ultraviolet
wavelength range and an integrated ultraviolet intensity within the
first ultraviolet wavelength range, with respect to a standard
solar radiation spectrum.
A eighth aspect of the invention is to provide an ultraviolet
measuring device comprising:
an ultraviolet sensitive element with spectral sensitivity to a
first wavelength range;
a storage unit which stores a standard intensity ratio; and
a correction unit which corrects an intensity measured by the
ultraviolet sensitive element on the basis of the standard
intensity ratio and a sun altitude correction factor to obtain a
response index,
wherein the standard intensity ratio is a ratio between a response
index and an integrated ultraviolet intensity within the first
ultraviolet wavelength range, with respect to a standard solar
radiation spectrum.
The details of the standard intensity ratio, the response index,
and the sun altitude correction factor may be the same as in the
third and fourth aspects.
The seventh and eighth aspects of the invention can be modified as
follows:
An ultraviolet measuring device comprising:
an ultraviolet sensitive element with spectral sensitivity to a
specific wavelength range;
a storage unit which stores a standard intensity ratio, the
standard intensity ratio being a ratio between a first integrated
ultraviolet intensity of a standard spectroscopic solar radiation
spectrum within a first ultraviolet wavelength range and a second
integrated ultraviolet intensity of the standard spectroscopic
solar radiation spectrum within a second ultraviolet wavelength
range or a third integrated ultraviolet intensity obtained from the
standard spectroscopic solar radiation spectrum and a response
curve; and
a correction unit which corrects an actually measured value of
solar ultraviolet intensity measured with the ultraviolet sensitive
element on the basis of the standard intensity ratio and a sun
altitude correction factor for the standard intensity ratio to
obtain an ultraviolet intensity within the second ultraviolet
wavelength range or an ultraviolet intensity related to the
response curve.
The ultraviolet intensity related to a specific response curve and
the third integrated ultraviolet intensity may be considered as a
response index.
According to the ultraviolet measuring device according to the
aspects of the invention, specific ultraviolet information about
ultraviolet rays within a specific range (the second ultraviolet
wavelength range) and about a response curve can be easily obtained
from a value measured by an ultraviolet sensitive element having
specific spectral characteristics. Therefore, such specific
ultraviolet information can be monitored conveniently and
constantly. Further, the total amount of ultraviolet rays can also
be obtained.
The ultraviolet measuring device may further comprise a sun
altitude information acquisition unit which acquires the sun
altitude information by which the conversion factor or the sun
altitude correction factor for the standard intensity ratio is
obtained. The ultraviolet measuring device may be provided with
latitude information and/or longitude information, and with date
and time information as the sun altitude information. Furthermore,
for example, the erythema curve may be applied as the response
curve as described above.
The conversion factor and the sun altitude correction factor for
the standard intensity ratio can be determined on the basis of the
light path length of the sunlight within the earth atmosphere and
ozone concentration information as described above. The light path
length and ozone concentration vary depending on the latitude
and/or the longitude and on the date and time. An accurate
ultraviolet intensity can be determined by acquiring such pieces of
information as sun altitude information with the sun altitude
information acquisition unit.
A ninth aspect of the invention is to provide an ultraviolet
measuring method, using an ultraviolet sensitive element with
spectral sensitivity to a specific wavelength range,
comprising:
measuring an ultraviolet intensity with the ultraviolet sensitive
element; and
correcting the measured ultraviolet intensity according to sun
altitude information for an arbitrary point in time so as to
predict an ultraviolet intensity at the point in time.
The sun altitude varies depending on the latitude and/or the
longitude, and date and time. The attenuation amount of the
sunlight upon transmission through the stratosphere and the
troposphere varies depending on the light path length. In addition,
the transmission coefficient varies depending on the wavelength.
Moreover, the attenuation amount upon transmission through the
ozone layer varies depending on the light path length within the
ozone layer and the ozone concentration of the ozone layer, in the
case of UVB wavelength range or of an ultraviolet wavelength range
related to the erythema curve.
The ultraviolet measuring method of the ninth aspect of the
invention utilizes the fact that ultraviolet intensity at a point
in time (which means "at a sun altitude") is influenced by the sun
altitude. Therefore, in the method, the ultraviolet intensity at an
arbitrary point in time is predicted by correcting the measured
ultraviolet intensity according to the sun altitude information at
the point in time. As a result, a specific ultraviolet information
can be acquired or predicted according to the location and the date
and time, regardless of the weather.
Furthermore, an integrated ultraviolet intensity over a period can
be calculated according to the ultraviolet measuring method of the
ninth aspect of the invention. And, an appropriate ultraviolet ray
protective agent can be decided based on the predicted integrated
amount of ultraviolet rays.
As described above, according to the method, an ultraviolet
intensity at an arbitrary point in time can be predicted. By
integrating the predicted ultraviolet intensity over a
predetermined period, it is possible to predict an integrated
ultraviolet intensity over the period in which an outing is
scheduled. Based on the predicted integrated ultraviolet intensity,
it is possible to select an ultraviolet ray protective agent
suitable for the outing and to block ultraviolet rays
effectively.
A tenth aspect of the invention is to provide an ultraviolet
measuring device comprising:
an ultraviolet sensitive element having spectral sensitivity to a
specific wavelength range;
a storage unit which stores sun altitude information for arbitrary
points in time; and
a correction unit which corrects an actually measured ultraviolet
intensity according to sun altitude information for an arbitrary
point in time so as to predict an ultraviolet intensity at the
point in time.
By using the ultraviolet measuring device of the tenth aspect of
the invention, it is possible to acquire or predict specific
ultraviolet information according to the location and the date and
time, regardless of the weather.
The ultraviolet measuring device may comprise a calculating unit
which calculates an integrated ultraviolet intensity over a
specified period, and a selection unit which select an ultraviolet
ray protective agent based on the predicted integrated ultraviolet
intensity. Effective ultraviolet ray protection can be realized by
the above configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a relationship diagram showing the spectral sensitivity
of an ultraviolet sensitive element, the spectrum of the sun, and
the erythema curve.
FIG. 2 is a schematic constitutional diagram showing a constitution
of an ultraviolet measuring device according to an embodiment of
the present invention.
FIG. 3 is a flow chart showing a flow of ultraviolet measurement
process in an ultraviolet measuring device according to an
embodiment of the invention.
FIG. 4 is a flow chart showing another flow of ultraviolet
measurement process in an ultraviolet measuring device according to
another embodiment of the invention.
DESCRIPTION OF THE PRESENT INVENTION
Hereinafter, an ultraviolet measuring method according to the
present invention will be explained in detail.
The ultraviolet rays having wavelengths not longer than 200 nm in
the sunlight are absorbed by oxygen and do not reach the surface of
the earth. Further, the ozone layer in the stratosphere absorbs the
ultraviolet rays having wavelengths of 200 nm through 360 nm.
Especially, the ultraviolet rays having wavelengths of 290 nm or
less are particularly efficiently absorbed by ozone. Accordingly,
ultraviolet rays (solar ultraviolet radiation) emitted by the sun
and reaching the surface of the earth consists of rays having
longer wavelengths than 290 nm. The ultraviolet rays having
wavelengths of 290 to 320 nm are called UVB, and the ultraviolet
rays having wavelengths of 320 to 400 nm are called UVA.
It is reported that the ratio between UVB and UVA in the solar
ultraviolet radiation is almost constant under any weather
conditions at the same time on the same day. The ratio varies
depending mainly on the amount of UVB absorbed by the ozone layer
of the stratosphere in the sky. Because the ultraviolet rays on the
ground have a narrower wavelength range, it is thought that
difference in scattering or reflection between the ultraviolet rays
having different wavelengths can be neglected and the wavelength
distribution is not strongly affected by the weather. Moreover, the
ultraviolet is not influenced by the height of the observation
point since even mountains are in the troposphere.
In an embodiment of the invention, an integrated ultraviolet
intensity within a specific wavelength range can be determined on
the basis of an intensity measured by a specific ultraviolet
sensitive element and a conversion factor corresponding to the sun
altitude. The conversion factor is a function of at least the sun
altitude. However, since the thickness of ozone layer differs
depending on the position on the earth, the conversion factor may
be a function of the latitude and/or the longitude, in addition to
the sun altitude. Further, the thickness of the ozone layer
changes, the conversion factor may depend on ozone layer
information. In another embodiment, a response index can be
determined on the basis of an intensity measured by a specific
ultraviolet sensitive element and a conversion factor corresponding
to the sun altitude. The basic principle is the same as recited
above. The term "response index" used herein refers to an index
indicating an extent of effect caused by ultraviolet rays. For
example, the effect may be, for example, an increase in possibility
of development of skin cancer, development of pigment spots,
development of erythema, or development of sunburn.
The conversion factor can be determined experimentally or
theoretically or by a combination thereof. For example, the
conversion factor can be determined by measuring the wavelength
distribution by a spectrophotometer, or by measuring the intensity
by a meter specific to a desired wavelength or desired response
index such as a UVA meter and a UVB meter. The data about
wavelength distribution disclosed in reference books or the like
are also usable. It is also possible to calculate the conversion
factor on the basis of factors such as the sun altitude, the
latitude, the longitude, the ozone information, and the solar
activity information. This calculation may be conducted
automatically on the observation point. Therefore, it is not always
necessary to determine conversion factors for respective sun
altitudes before a measurement.
The term "an integrated ultraviolet intensity" used herein refers
to an ultraviolet intensity integrated along the wavelength axis,
unless specified otherwise. Similarly, the term "an integrated
ultraviolet intensity within a wavelength range" refers to an
ultraviolet intensity integrated over the wavelength range.
Further, the term "light path length" used herein refers to a light
path length along which the light passes through the ozone layer,
unless specified otherwise. Accordingly, the light path length
refers to a light path length only within the ozone layer, unless
specified otherwise.
In an ultraviolet measuring method according to an embodiment of
the invention, a calibrated value of sunlight intensity actually
measured (in the troposphere) by an ultraviolet sensitive element
with specific spectral sensitivities (for example, 200 to 400 nm)
is corrected according to a standard intensity ratio and a sun
altitude correction factor (a sun altitude correction factor for
the standard intensity ratio), so that ultraviolet information
within specific wavelength range is obtained. The standard
intensity ratio is a ratio between an integrated ultraviolet
intensity obtained from the spectrum of the sun and another
integrated ultraviolet intensity within a specific wavelength range
(a second integrated ultraviolet intensity in a second ultraviolet
wavelength range of the spectroscopic solar radiation spectrum, or
a third integrated ultraviolet intensity obtained from the solar
ultraviolet radiation spectrum and a specific response curve). That
is, when, for example, the integrated ultraviolet intensity within
a specific range is the ultraviolet intensity (erythema ultraviolet
intensity) which is obtained from the solar spectrum and the
erythema curve, the erythema ultraviolet amount and the UV index
can be obtained on the basis of the erythema ultraviolet intensity
obtained from an actually measured value.
The UV index can be determined by: (1) converting the erythema
ultraviolet intensity to the erythema ultraviolet amount per hour
(mJ/cm.sup.2), then (2) dividing the obtained value by 10.
In an ultraviolet measuring method according to another embodiment
of the invention, an obtained ultraviolet intensity is corrected
according to the sun altitude information for an arbitrary point in
time, so that the ultraviolet intensity at the point in time is
predicted. For example, in predicting ultraviolet intensity at an
arbitrary point in time (at a second point in time) from the
ultraviolet intensity measured at a certain point in time (at a
first point in time), the ultraviolet intensities at the second
point in time can be corrected with sun altitude information (solar
ultraviolet information). The sun altitude information may include
pieces of information about the relationship between the sun
altitude and the ultraviolet intensity at the first and second
points in time, a weather factor, and the sun altitude correction
factor.
Hereinafter, a correction method is described in detail, by which
an amount of specific ultraviolet rays (ultraviolet intensity
within a specific wavelength range) UV(.lamda.) is obtained based
on an actually measured value UV0 (.alpha..sub.1) at a sun altitude
.alpha..sub.1 which has been so calibrated that UV0 (.alpha..sub.1)
corresponds to the total amount of solar ultraviolet radiation.
An integrated ultraviolet intensity UV1 (.theta.) within a target
specific range (a second integrated ultraviolet intensity of
spectroscopic solar radiation spectrum within a second ultraviolet
wavelength range, or a third integrated ultraviolet intensity
obtained from the solar ultraviolet radiation spectrum and a
specific response curve) at a standard sun altitude .theta. is
obtained by the following formula (1):
UV1(.theta.)=.SIGMA.F(.lamda.)R(.lamda.,.theta.).DELTA..lamda.
Formula (1)
In the formula, F represents a weighting factor (for example, the
erythema curve), and R(.lamda.,.theta.) represents a spectroscopic
radiation intensity at a standard sun altitude .theta..
.DELTA..lamda. represents the unit wavelength interval of the
spectroscopic radiation spectrum.
Then, an integrated ultraviolet intensity UV2 (a first integrated
ultraviolet intensity) within a predetermined ultraviolet
wavelength range at the standard sun altitude .theta. obtained from
the solar spectrum is represented, for example, by the following
formula (2). The predetermined ultraviolet wavelength range may be,
for example, wavelength range of 290 to 400 nm.
UV2(.theta.)=.SIGMA.R(.lamda.,.theta.).DELTA..lamda. Formula
(2)
In the formula, R(.lamda.,.theta.) represents a spectroscopic
radiation intensity at the standard sun altitude .theta..
As recited above, UV0 is measured at the sun altitude
.alpha..sub.1. The integrated ultraviolet value UV1(.alpha..sub.1)
within the target specific wavelength range at the sun altitude
.alpha..sub.1 can be calculated from a standard intensity ratio
between UV1(.theta.) and UV2(.theta.) and the sun altitude
correction factor P(.alpha..sub.1) for the standard intensity
ratio, as expressed by the following formula (3).
UV1(.alpha..sub.1)=UV0(.alpha..sub.1).times.(UV1(.theta.)/UV2(.theta.)).t-
imes.P(.alpha..sub.1) Formula (3)
The erythema ultraviolet intensity G (.alpha..sub.1) derived from
the erythema curve E(.lamda.) can be represented by the following
formula (4):
G(.alpha..sub.1)=UV0(.alpha..sub.1).times.(UV1(.theta.)/UV2(.theta.)-
).times.P(.alpha..sub.1) Formula (4)
In this case, UV1(.theta.) is calculated by the equation,
UV1(.theta.)=.SIGMA.E(.lamda.) R(.lamda., .theta.) .DELTA..lamda..
UV1(.theta.) is a standard erythema ultraviolet intensity.
The sun altitude correction factor P(.alpha..sub.1) for the
standard intensity ratio (UV1(.theta.)/UV2 (.theta.)) can be
obtained from the light path length and the transmission
coefficient upon transmission of the sunlight through the air. The
transmission coefficient is influenced by ozone absorption, thus
dependent on the wavelength. The light path length, along which the
sunlight passes through the air, can be calculated from the sun
altitude.
That is, the sun altitude correction factor P(.alpha..sub.1) can be
obtained from the attenuation rate which can be calculated from the
light path length and the transmission coefficient, wherein the
light path length is a function of the sun altitude. Hereinafter,
the details of determination of the sun altitude correction factor
P(.alpha..sub.1) is explained.
Sun Altitude and Light Path Length within an Ozone Layer
The light path length along which the sunlight passes through the
ozone layer in the stratosphere is calculated from the sun altitude
which depends on the date and diurnal motion.
Calculation of Sun Altitude
The sun altitude (zenith angle Z) is obtained by the following
formula: cos Z=cos D' cos L'+sin D' sin L' cos H Formula (5)
In the formula, L' represents the colatitude of the observation
point (the complementary angle of latitude L); D' represents the
polar distance angle (the complementary angle of the celestial
declination D); and H represents the hour angle.
The polar distance angle D' is calculated by the following formula
(6): cos D'=sin 23.5.degree. sin .alpha..sub.2 Formula (6)
.alpha..sub.2 represents an angle between a line connecting the
earth and the sun on the observation day and a line connecting the
earth and the sun at the vernal equinox of the year. .alpha..sub.2
can be expressed by .alpha..sub.2=n360.degree./365.25 (n is a
number of days that has elapsed since the equinox).
The hour angle H is obtained by the following formula (7):
H=.+-.360.degree. t/24 hours Formula (7)
Here, t represents hours that have elapsed since the meridian
passage, wherein a negative sign indicates that the observation is
conducted before the meridian passage. The time at the meridian
passage can be calculated by correcting the local standard time of
the area by the difference in longitude between the observation
point and the standard longitude. In order to make the hour angle
more accurate, the hour angle can be corrected according to the
equation of time.
With regard to the way of getting the above-described information,
the date and time can be acquired from a clock. If the observation
points are limited to a local area, the latitude may have been
inputted as the position information. Alternatively, the position
information can be acquired at any time with a position measurement
device utilizing information from artificial satellites.
Attenuation Amount According to Light Path Length
The absorption coefficient, which is a major factor in determining
the attenuation rate of ultraviolet rays upon transmission through
the air, can be obtained from measured solar radiation spectra at
different sun altitudes. The ultraviolet from the sun is attenuated
by absorption by ozone in the stratosphere, and absorbed,
scattered, or reflected in the troposphere depending on the state
of the atmosphere. Scattering (Mie scattering) by clouds is
scarcely dependent on the wavelength, which is in contrast to
scattering (Rayleigh scattering) by air molecules.
If attenuation coefficients for respective wavelengths region have
been determined, not only an erythema ultraviolet amount, but also
an amount of specific ultraviolet (specific ultraviolet
information) can be estimated based on the relationship between the
actually measured value and the sun altitude. One of the
coefficients which determine the attenuation rate is the absorption
coefficient upon absorption of ultraviolet by ozone. This
absorption coefficient is significant only in the wavelength range
of 320 nm or less. The other coefficient is scattering coefficient.
The scattering coefficient is significant in the whole ultraviolet
wavelength range.
Calculation of Sun Altitude Correction Factor P(.alpha..sub.1)
(Influence of the Sun Altitude on Ozone Absorption)
Calculation of the light path length: In the following, the sun
altitude is represented by .theta..sub.0 (elevation angle), the
radius of the earth is represented by r.sub.0 (6400 km), the height
of the highest point of the ozone layer is represented by r.sub.2,
and the height of the lowest point of the ozone layer is
represented by r.sub.1. The light path length x(.theta..sub.0) in
the ozone layer is represented by the following formula:
x(.theta..sub.0)=-r.sub.0 sin(.theta..sub.0)+ {square root over (
)}[(r.sub.0
sin(.theta..sub.0)).sup.2+(r.sub.2.sup.2+2r.sub.2r.sub.0)]-{-r.sub.0
sin(.theta..sub.0)+ {square root over ( )}[(r.sub.0
sin(.theta..sub.0)).sup.2+(r.sub.1.sup.2+2r.sub.1r.sub.0)]} Formula
(8)
The light path length is considered as a function of the sun
altitude. For example, under the following conditions r.sub.1=20
km, and r.sub.2=40 km, the light path length can be calculated as
follows: x(80.degree.)=20.3 km, x(30.degree.)=39.47 km,
x(15.degree.)=72.75 km, and x (0.degree.)=210.3 km.
Calculation of Attenuated Amount:
The amount "I" attenuated by absorption can generally be expressed
by using the light path length as follows: I=I.sub.0
exp(-kx(.theta..sub.0)) Formula (9)
In the formula, I.sub.0 is the intensity of an incident UV, and k
is an absorption coefficient, which can be considered as a function
of the wavelength. However, k is considered to be a constant for
the narrow wavelength region such as UV region except the
absorption of UVB (and UVC) in the ozone layer.
In the following formulae, a transmittance of the whole UV through
the stratosphere and troposphere is represented by
Tr(.theta..sub.0), an absorption coefficient of ultraviolet in the
UVB range in the ozone layer is represented by kb(.lamda.b) (it is
assumed that the transmittance of the ultraviolet in the UVB range
in the other layers than the ozone layer is equal to the
transmittance of the whole UV, which is Tr(.theta..sub.0)). The
incident intensity of the whole UV entering the stratosphere is
represented by I.sub.0 (.theta..sub.0) and the incident intensity
of the whole UVB entering the stratosphere is represented by
Ib.sub.0 (.theta..sub.0).
The attenuated Ib(.theta..sub.0) is expressed by the following
formula (10): Ib(.theta..sub.0)=Ib.sub.0
exp(-kb(.lamda.b)x(.theta..sub.0)).times.Tr(.theta..sub.0) Formula
(10)
The attenuated I(.theta..sub.0) is represented by the following
formula (11): I(.theta..sub.0)=I.sub.0Tr(.theta..sub.0) Formula
(11)
When the sun altitude is .theta..sub.0 and the transmission
distance is x(.theta..sub.0), the ratio of UVB to UV after the
absorption is represented by the following formula (12):
Ib(.theta..sub.0)/I(.theta..sub.0)=(Ib.sub.0/I.sub.0)exp(-kb(.lamda.b)x(.-
theta..sub.0)) Formula (12)
The UVB/UV ratio differs according to the season. For example, at
Tokyo, a ratio of UVB/UV around the meridian passage (80.degree.)
in the summer is 5.5%, and the ratio of UVB/UV at the meridian
passage (30.degree.) in the winter is 3%, wherein the ratios have
been obtained from the spectroscopic irradiance of rays coming
directly from the sun without scattering. However, as the sun
altitude is low in the morning to reduce the amount of short
wavelength ultraviolet, the ratio of UVB/UV is about 1% even in the
summer. Since the UVB/UV ratio can be calculated, by using the
ratio as of the observation time point, it is possible to estimate
the UVB amount based on the amount of the whole ultraviolet. In the
summer, since the variation in the concentration of the ozone layer
is smaller than in spring, the concentration of the ozone layer can
be considered almost constant.
Since the erythema ultraviolet has further shorter wavelength than
that of UVB, the variation in the ratio of the erythema ultraviolet
to the whole UV is more significant than the variation in the ratio
of UVB to the whole UV.
(Ib.sub.0/I.sub.0) and kb(.lamda.b) can be obtained by comparing
irradiances of spectroscopic solar radiation measured at different
sun altitudes .theta..sub.0
In an embodiment, spectroscopic ultraviolet radiation intensities
Ib(.theta..sub.1) and I(.theta..sub.1) are measured at a highest
sun altitude (.theta..sub.1) around the summer solstice. Similarly,
spectroscopic ultraviolet radiation intensities Ib(.theta..sub.2)
and I(.theta..sub.2) are measured at a lowest sun altitude
(.theta..sub.2) around the winter solstice. From these values,
ratios Ib(.theta..sub.1)/I(.theta..sub.1) and
Ib(.theta..sub.2)/I(.theta..sub.2) are obtained. By comparing the
ratios, .alpha.=(Ib.sub.0/I.sub.0) and .beta.=kb(.lamda.b) with
respect to the erythema ultraviolet or the UVB can be obtained. As
a result, if the measured value I(.alpha..sub.1) is obtained with
information on the sun altitude .alpha..sub.1 (as .theta..sub.0),
it is possible to calculate the UVB or erythema ultraviolet
intensity as follows:
Ib(.alpha..sub.1)=I(.alpha..sub.1).alpha.exp(-.beta.x(.alpha..sub.1))
Formula (13)
The above formula can be normalized by the standard sun altitude
.gamma.(as .theta.) to cause the following formula (14):
Ib(.alpha..sub.1)=I(.alpha..sub.1)(Ib(.gamma.)/I(.gamma.))exp
[-.beta.(x(.alpha..sub.1)-x(.gamma.))] Formula (14)
Accordingly, the sun altitude correction factor P(.alpha..sub.1) is
represented by the following formula (15):
P(.alpha..sub.1)=exp[-.beta.(x(.alpha..sub.1)-x(.gamma.))] Formula
(15)
Then, the above formulae are combined to form the following formula
(16).
Ib(.alpha..sub.1)=I(.alpha..sub.1)(Ib(.gamma.)/I(.gamma.))P(.alpha..sub.1-
) Formula (16)
Based on these formulae, an ultraviolet intensity within the UVB
region or an erythema ultraviolet intensity at the sun altitude
.alpha..sub.1 can be obtained by the following formula (17): UVB
intensity (at the sun altitude .alpha..sub.1)=measured value (at
the sun altitude .alpha..sub.1).times.standard intensity
ratio.times.sun altitude correction factor Formula (17) Erythema
ultraviolet intensity (at the sun altitude .alpha..sub.1)=measured
value (at the sun altitude .alpha..sub.1).times.standard intensity
ratio.times.sun altitude correction factor Formula (18)
As described above, an actually measured value UV0(.alpha..sub.1)
at a sun altitude .alpha..sub.1 is multiplied by a standard
intensity ratio (UV1 (.gamma.)/UV2(.gamma.)) at a standard sun
altitude .gamma.(as .theta.), and further multiplied by a sun
altitude correction factor P(.alpha..sub.1) at the sun altitude
.alpha..sub.1 to obtain a UVB intensity at the sun altitude
.alpha..sub.1 or an erythema ultraviolet intensity at the sun
altitude .alpha..sub.1.
The intensity to be calculated may be an intensity within a
specific ultraviolet wavelength range (for example, UVB) or an
erythema ultraviolet intensity obtained from a specific response
curve (for example, the erythema curve). Such intensities can be
calculated by using respective standard ratios at the standard sun
altitude .gamma.(as .theta.) and respective sun altitude .gamma.(as
.theta.).
The UV index is represented by one tenth of the amount of erythema
ultraviolet. The amount of erythema ultraviolet is an amount of
ultraviolet per hour converted according to the erythema curve
shown in FIG. 1, and is generally represented by the following
formula (19): Erythema ultraviolet amount=erythema
curve.times.spectroscopic solar ultraviolet irradiance.times.3600
seconds Formula (19)
In other words, the following formula is satisfied. (Erythema
ultraviolet amount)/10=UV index Formula (20) Standard intensity
ratio, Ib(.gamma.)/I(.gamma.) can be represented by the following
formula. Ib(.gamma.)/I(.gamma.)=UV index.times.10/the whole
ultraviolet intensity/3600 seconds Formula (21)
Accordingly, the UV index can be expressed by the following
formula. UV index=Actually measured intensity
UV0(.mu.W/cm.sup.2).times.(UV index/the whole ultraviolet amount,
at a standard sun altitude).times.Sun altitude correction factor
Formula (22)
Thereby, the erythema ultraviolet amount can be calculated from the
actually measured value of solar ultraviolet radiation (total
amount of ultraviolet) on the basis of the standard intensity ratio
and the sun altitude correction factor, which are obtained from the
positional information about the observation point (latitude
information and longitude information) and the date and time
information. The UV index can be obtained in the same way.
When the sun altitude correction factor P(.alpha..sub.1) is
determined, ozone concentration information can be considered. In
other words, the sun altitude correction factor P(.alpha..sub.1)
can be modified according to changes in the ozone concentration.
The modification may be conducted by modifying the absorption
coefficient.
If the standard intensity ratio is measured at an ozone
concentration Oz1 and observation is conducted at an ozone
concentration of Oz2, the transmittance can be corrected according
to a correction factor:-exp (-standard absorption
coefficient.times.Oz2/Oz1.times.light path length in the ozone
layer). This is because the absorption can be expressed by "the
absorption coefficient.times.the concentration." The National
Aeronautics and Space Administration (NASA) provides daily data on
the ozone concentration, which is measured by artificial
satellites, (TOMS: Total Ozone Mapping System). The data supplied
by NASA can be used in the invention. Daily measured values may be
used or a mean of values over several months or six months, which
takes seasonal variations into consideration, may be used as the
data on the ozone concentration.
Hereinafter, details are explained about the prediction of
ultraviolet information for an arbitrary point in time on the basis
of an obtained ultraviolet intensity. The prediction method
includes converting the measured ultraviolet intensity according to
solar altitude information for the point in time. The obtained
ultraviolet intensity may be a specific ultraviolet intensity
obtained by the above-described conversions, corrections, or
modifications. Alternatively, the obtained ultraviolet intensity
may have been obtained in another way.
In the first place, an almost linear relationship is established
between the sun altitude (elevation angle) and the ultraviolet
intensity in clear weather and clear atmosphere (for example, S.
Yagi, PhotoMed. Photobiol. vol 25 p 55 (2003)). Based on the
relationship, regardless of the season, the ultraviolet intensity
in clear weather can be predicted from the sun altitude, which is
determined by the latitude, the longitude, and the date and the
time. The above prediction is conducted in clear weather. Regarding
a prediction in a kind of weather other than clear weather, the
prediction is possible in a manner recited below. A weather
coefficient is determined by actual measurement. Specifically, the
weather coefficient is obtained by dividing the intensity measured
in a kind of weather at a sun altitude by an intensity predicted
for the sun altitude based on the above relationship. It is
possible to predict the ultraviolet intensity in the kind of
weather at an arbitrary point in time by predicting an ultraviolet
intensity at the arbitrary point in time on the basis of the above
relationship and multiplying the predicted ultraviolet intensity by
the weather coefficient.
It is also possible to predict an erythema ultraviolet amount and a
UV index within an arbitrary period of time from an ultraviolet
intensity (erythema ultraviolet intensity) obtained at a point in
time, utilizing the above method.
Hereinafter, an example is specifically explained. In the example,
an erythema ultraviolet intensity is obtained from an actually
measured value, then an erythema ultraviolet amount E is acquired
on the basis of the obtained erythema ultraviolet intensity to
obtain a UV index.
Here, solar ultraviolet radiation is measured by an ultraviolet
measuring device which utilizes an ultraviolet sensor (an
ultraviolet sensor mounted on UV CAREMATE manufactured by Fuji
Xerox Co., Ltd.) comprising a polycrystalline gallium nitride
semiconductor, so that UV0 is obtained from the actual measurement.
The ultraviolet measuring device is adjusted in such a way that an
actually measured value is identical with a total amount of
ultraviolet of 290 to 400 nm emitted from a standard light source.
The sensitivity range of the device is 280 to 410 nm in this case.
However, a device having a sensitivity range of, for example, 330
to 400 nm can be used for measuring the ultraviolet intensity
within the wavelength range of 290 nm through 400 nm.
In order to obtain UVB from an actually measured value, the amount
of UVB is obtained in the first place.
In the following, the horizontal data measured by the
Electrotechnical Laboratory (currently National Institute of
Advanced Industrial Science and Technology) at Tanashi-shi, Tokyo,
Japan is used and a spectral measured value at a sun altitude
(elevation angle) of 77.degree. is assumed to be a standard
sunlight ultraviolet ray.
Approximately at the summer solstice (77.degree., on Jun. 23,
1979), UVB within a range of 290 to 320 nm is represented by the
following formula (23):
Ib(77)/I(77)=0.0132=(Ib.sub.0/I.sub.0)exp(-kb(.lamda.b)x(77))
Formula (23)
Thus, a standard ratio (standard intensity ratio) of UVB to the
total amount of ultraviolet at the sun altitude of 77.degree. is
0.0132.
In order to obtain the UV index from the actually measured value,
the erythema ultraviolet amount E is corrected according to sun
altitude information. Here, the sun altitude correction factor for
the standard intensity ratio of (the erythema ultraviolet
intensity/whole UV) is obtained from the atmospheric transmission
coefficient and the light path length according to the sun
altitude.
In the following, the horizontal data of the Electrotechnical
Laboratory at Tanashi-shi, Tokyo, Japan is used. The irradiance
within the full range of 290 to 400 nm is used as the UV
intensity.
Around the summer solstice (77.degree., on Jun. 23, 1979), the
following formula is satisfied.
Ib(77)/I(77)=0.0050=(Ib.sub.0/I.sub.0)exp(-kb(.lamda.b)x(77))
Formula (24)
Thus, a standard erythema ultraviolet ratio (standard intensity
ratio) at the sun altitude of 77.degree. to the total amount of
ultraviolet is 0.005.
Around the winter solstice (31.degree., on Dec. 22, 1979), the
following formula (22') is satisfied.
Ib(31)/I(31)=0.0023=(Ib.sub.0/I.sub.0)exp(-kb(.lamda.b)x(31))
Formula (22')
Therefore, a mean absorption coefficient kb(.lamda.b) of the
erythema ultraviolet range in the ozone layer is given by the
following formula (25):
.function..lamda..times..times..times..function..function..function..time-
s..times..times. ##EQU00001##
Moreover, Ib.sub.0/I.sub.0 is given by the following formula (26):
Ib.sub.0/I.sub.0=0.0050/exp(-kb(.lamda.b)x(77))=0.0122 Formula
(26)
As a result, a ratio C between the erythema ultraviolet and UV at
an arbitrary sun altitude .theta..sub.0 is represented as a
function of the transmission distance x(.theta..sub.0) by the
following formula (27):
C=Ib(.theta..sub.0)/I(.theta..sub.0)=(0.0122)exp(-0.0434.times.x(.theta..-
sub.0)) Formula (27)
The ratio of the UVB to the whole UV can be obtained by a similar
method.
Then, the light path length in the ozone layer according to the sun
altitude is calculated to obtain sun altitude dependency of the
ratio between the erythema ultraviolet and UV. The following values
are used in the calculation: 6400 km as the radius r.sub.0 of the
earth, 40 km as the height r.sub.2 of the upper limit of the ozone
layer, 20 km as the height r.sub.1, of the lower limit of the ozone
layer. .theta..sub.0 represents the sun altitude (elevation angle).
As the standard ratio, used is the ratio between the amount of the
erythema ultraviolet and the total amount of ultraviolet obtained
from the integrated ultraviolet intensity of the above-described
standard solar radiation spectrum (the meridian passage altitude of
77.degree. according to the horizontal data at Tanashi-shi, Tokyo,
Japan). The light path length, for example at the sun altitude of
30.degree., is 40 km. Accordingly, the sun altitude correction
factor C is 0.44. Moreover, the sun altitude correction factor C is
0.78 at the sun altitude of 50.degree., corresponding to a light
path length in the ozone layer of 26 km.
Accordingly, for example, an erythema ultraviolet intensity at the
sun altitude of 30.degree. on the same observation day is obtained
by the following formula (18'): Erythema ultraviolet intensity
(30.degree.)=Actually measured value UV0
(30.degree.).times.0.005.times.0.44 Formula (26')
Therefore, an erythema violet intensity can be expressed by the
following formula. Erythema ultraviolet amount
(mJ/cm.sup.2)=Actually measured value UV0
(30.degree.)(.mu.W/cm.sup.2).times.1/1000.times.0.005.times.360-
0s.times.0.44 Formula (28)
As the UV index is one tenth of the erythema ultraviolet amount, if
the actually measured value UV0(.alpha..sub.1) is, for example,
5000 .mu.W/cm.sup.2, the UV index is 9 in the case of a sun
altitude of 78.degree. (=.alpha..sub.1), and the UV index is 4 in
the case of a sun altitude of 30.degree.. Accordingly, if the
location and the date and time are given, the amount of erythema
ultraviolet and a UV index can be obtained from a measured UV
value.
The formulae (18') and (28) can be considered as expressing a
conversion factor. Accordingly, this embodiment may also be
considered as an embodiment of the ultraviolet measuring method
which uses a conversion factor.
The margin of error of these relationships expressed by the
formulae is within .+-.20%, regardless of the weather. Moreover,
UVB and UVA can be separately obtainable from the actually measured
value of the total amount of ultraviolet according to the
above-described method. UVB can be obtained in the same manner as
in the case of the erythema ultraviolet. Specifically, the
atmospheric transmission coefficient is obtained on the basis of
comparison of the ratio between the UVB and the total amount of UV
at a standard sun altitude and the ratio between the UVB and the
total amount of UV at another sun altitude. UVA can be calculated
by the following relationship: UVA=Actually measured UV
amount-UVB.
Subsequently, an example is described in which an erythema
ultraviolet intensity at an arbitrary point in time is obtained
from an obtained erythema ultraviolet intensity through a
correction by sun altitude information for the arbitrary point in
time.
As an example, assuming that the measured value of ultraviolet
intensity at a sun altitude of 30.degree. on a fine day in summer
is 2500 .mu.W/cm.sup.2, and that an estimated ultraviolet intensity
at that time is 3000 .mu.W/cm.sup.2, the weather coefficient can be
2500/3000. It is also assumed that an erythema ultraviolet
intensity after the sun altitude correction is 5 .mu.W/cm.sup.2 at
the sun altitude. If an estimated intensity at several hours later
at a sun altitude of 60.degree. is 6000 .mu.W/cm.sup.2 and an
erythema ultraviolet intensity at that time predicted based on the
estimated intensity is 24 .mu.W/cm.sup.2, the estimated erythema
ultraviolet intensity of 24 .mu.W/cm.sup.2 is multiplied by the
weather coefficient (2500/3000) to obtain a predicted erythema
ultraviolet intensity (20 .mu.W/cm.sup.2) at a sun altitude of
60.degree. on the same day. Moreover, an approximate weather
coefficient can be obtained from the weather forecast.
Furthermore, an integrated erythema ultraviolet intensity within an
arbitrary period can be obtained by integrating the obtained
erythema ultraviolet intensity over the period.
Moreover, it is possible to suggest the kind of ultraviolet
protective agent (sunscreen cosmetics) which provides a suitable
protection against UV, based on the amount of erythema ultraviolet
and the integrated erythema ultraviolet intensity obtained as
described above. For example, the time required for the skin to be
reddened by UV can be calculated based on the Minimum Erythema Dose
(MED), and a Sun Protection Factor (SPF value) or Protection Grade
of UVA (PA) of the ultraviolet protecting agent adequate for
required UV protection level can be determined. Accordingly, for
example, a suitable ultraviolet protecting agent can be selected
before leaving home, based on ultraviolet information obtained from
the schedule of the day. In this way, efficient UV protection can
be realized.
Here, the SPF value and the PA value are obtained from the amount
of erythema ultraviolet and the integrated erythema ultraviolet
intensity, for example, in the following way.
The SPF value indicates the level of the erythema ultraviolet
protection. First, an erythema ultraviolet intensity integrated
over a scheduled period is obtained in the above-explained manner.
A sun-screen agent can be determined which reduces the erythema
ultraviolet dose to not more than the Minimum Erythema Dose (MED:
an ultraviolet amount just sufficient for reddening the skin) of
the person. For example, if the scheduled outdoor period is four
hours and an erythema ultraviolet amount over the scheduled period
is 400 mJ/cm.sup.2 (a UV index of 10 is assumed to be maintained
for four hours) and the person (whose skin is easily reddened) has
a MED of 10 mJ/cm.sup.2, then SPF40 can be selected. This is
because the protection has to attenuate the erythema ultraviolet at
a rate of 1/40.
Similarly, regarding PA, a required protection against a UVA
intensity over a specified period is expressed in three levels. If
a UVA intensity of 7500 .mu.W/cm.sup.2 is considered a maximum
degree of 10, the PA+ level corresponds to degrees 2 to 3 which
indicates a UVA intensity of 1000 to 2500 .mu.W/cm.sup.2, the PA++
level corresponds to degrees 4 to 7 which indicates a UVA intensity
of 2500 to 5500 .mu.W/cm.sup.2, and PA+++ level corresponds to
degrees 8 to 10 which indicates a UVA intensity of 5500
.mu.W/cm.sup.2 or larger. A predicted value of the UVA is obtained
by subtracting an UVB intensity from the whole ultraviolet
intensity, wherein the UVB intensity is obtained from the standard
intensity ratio between the UVB and the whole ultraviolet and the
sun altitude correction factor in the same manner as in the case of
the erythema ultraviolet amount. As a simpler method, the amount of
the whole ultraviolet may be used as the UVA amount. For example,
it is proposed to use a sunscreen with the PA++ level when the
predicted UVA intensity is 4000 .mu.W/cm.sup.2.
Hereinafter, the ultraviolet measuring device according to an
embodiment of the invention will be explained in more detail, with
reference to figures. Components having a substantially similar
function shown in more than one figure is indicated by the same
reference number in the figures. The explanation of the same
component with the same reference number as an already-explained
component is occasionally omitted.
FIG. 2 is a schematic constitutional diagram showing a constitution
of an ultraviolet measuring device according to an embodiment of
the present invention.
The ultraviolet measuring device 10 according to the embodiment
comprises: a liquid crystal display 16 (display device) which
displays various kinds of information; an ultraviolet sensitive
element 18 which detects ultraviolet information in a form of a
physical quantity of the ultraviolet; an operation panel 20
(operation device: for example, a power supply switch, a mode
change switch, and a set switch) to which various kinds of
information is inputted by the user of the ultraviolet measuring
device 10; and an input-output terminal 22 through which the
ultraviolet information indicating the ultraviolet intensity
measured by the ultraviolet measuring device 10 is outputted and
through which various kinds of information is inputted from an
information terminal (not shown).
The ultraviolet sensitive element 18 may be an ultraviolet
sensitive element produced by attaching a visible-ray-cut filter to
a photodiode having a sensitivity in visible-ray range such as a
photodiode comprising GaP or Si having a sensitivity in visible-ray
range. Alternatively, the ultraviolet sensitive element 18 may be
an ultraviolet sensitive element comprising an oxide semiconductor
such as titanium oxide or zinc oxide. Especially, the ultraviolet
sensitive element 18 may particularly preferably an ultraviolet
sensitive element comprising a nitride-based compound
semiconductor, which has a fast optical response, an absorption
range adjustable by changing the composition, and excellent design
properties in terms of size, color, and the like. Such an
ultraviolet sensitive element does not require much space in a
display section and the element can be compact and thin.
In the embodiment, a proportion of scattered solar ultraviolet in
the ultraviolet radiation to be detected is significant. Therefore,
However, the incidence angle characteristics of the ultraviolet
sensitive element 18 preferably meet the Lambert's cosine law. The
scattering coefficient is represented according to the law of
Rayleigh. In other words, the scattering coefficient is expressed
by the following formula. Scattering coefficient=a
constant/(wavelength).sup.4. The scattering coefficient for a
wavelength of 300 nm is 1.7 times the scattering coefficient for a
wavelength of 340 nm under fine weather. The scattering
coefficients for those wavelengths are five to eight times the
scattering coefficient for a wavelength of 500 nm. Therefore, the
scattering effect is significant in the case of ultraviolet rays
having a short wavelength. Moreover, the displayed figures is a
figure so corrected as to indicate an integrated ultraviolet amount
of the spectroscopic solar radiation spectrum.
In the embodiment, a display module with a trade name: SEK1054B,
manufactured by Seiko Epson Corporation is used as the liquid
crystal display 16. The display module is a dot-matrix-type liquid
crystal display module, and has a display surface of 96.times.32
dots, on which arbitrary information such as characters and graphs
can be displayed. For example, on the spot after a measurement, a
simple graph can be displayed on the display, and irradiance
distribution and the like can be so displayed without outputting
the data to the external input-output device (not shown) that the
distribution and the like can be grasped intuitively. Not only the
above-described display, but also all other displays such as other
types of liquid crystal display, organic electroluminescent (EL)
displays, plasma displays, and CRT displays can be used as the
display 16.
The ultraviolet measuring device 10 comprises an internal circuit
32. The internal circuit 32 comprises: a central processing unit
(CPU) 34 (CPU: a correction device) which controls all the
operations of the ultraviolet measuring device 10; a memory 38
(storage device) which store various information; an analog/digital
converter 40 (Hereafter, called "A/D converter") which converts
inputted analog signals into digital data for output; an amplifier
circuit 42 which amplifies an inputted analog signal; a
rechargeable battery 44 which supplies driving electric power to
sections in the internal circuit 32; and a power supply control
circuit 46 which controls the voltage and the like of the current
supplied to the rechargeable battery 44 when the battery 44 is
recharged. In FIG. 2, connecting lines representing electric power
supply lines from the rechargeable battery 44 to the sections in
the circuit 32 are not shown for the sake of simplicity of the
figure.
The internal circuit 32 comprises, as a sun altitude information
acquisition unit, a Global Positioning System (GPS) receiver 24
which acquires position information; and a calendar/clock 36 which
provides information about the date and time.
The GPS receiver 24 is connected to the CPU 34. The GPS receiver 24
comprise an antenna (not shown) which receives the electric waves
from plural satellites (generally four satellites) orbiting the
earth. The time required for the electric waves to travel the
distance between a satellite and the antenna is used for
calculating the distance between the satellite and the antenna. In
this way, the distance between the antenna and each satellite is
determined so that the position information (in the embodiment,
one-dimensional information of latitude and longitude) is obtained.
Thereby, the CPU 34 can acquire the position information at any
time.
The calendar/clock 36, which provides information on the date and
time, is connected to the CPU 34. The CPU 34 can acquire the date
and time information (month, day, and time) from the calendar/clock
36 at any time. The calendar/clock 36 may be included in the CPU
34, and the time information can be acquired by using software.
Moreover, the memory 38 is connected to the CPU 34 which can store
and read various kinds of information in the memory 38.
Furthermore, the liquid crystal display 16 is connected to the CPU
34 which can order the display 16 to display various kinds of
information. The switches in the operation panel 20 are also
connected to the CPU 34 which can detect at any time whether the
switches are pressed by the user.
The sensor output terminal of the ultraviolet sensitive element 18
is connected to the input terminal of the A/D converter 40 through
the amplifier circuit 42. The output terminal of the converter 40
is connected to the CPU 34.
Moreover, the data input-output terminal 22 is connected to the CPU
34, wherein the CPU 34 can input and output various kinds of
information through the data input-output terminal 22. Here, the
data input-output terminal 22 is connected not only to the CPU 34,
but also directly to the memory 38. Thereby, the ultraviolet
measuring device 10 has a configuration in which various kinds of
information can be written into the memory 38 directly from the
outside through the data input-output terminal 22, and can be
retrieved to the outside directly from the memory 38. Moreover, the
data input-output terminal 22 is also connected to the rechargeable
battery 44 through the power supply control circuit 46. In the
ultraviolet measuring device 10, the voltage and the like are
controlled by the power supply control circuit 46, and the circuit
46 recharges the rechargeable battery 44 in accordance with signals
from the data input-output terminal 22.
In the ultraviolet measuring device 10, the CPU 34 is required to
operate stably at any time. Therefore, in order to drive the CPU 34
with the rechargeable battery 44 as in the embodiment, the CPU 34
has to be capable of operating at a low electric power consumption
and to have enough processing performance. In accordance with the
necessity, a CPU with a trade name "H8/3827R" manufactured by
Hitachi Semiconductor is used as the CPU 34 in this embodiment. The
H8/3827R has a built-in calculation program, a built-in volatile
memory for primary storage, and a built-in analog/digital converter
circuit (corresponding to the A/D converter 40 in FIG. 2).
Therefore, the number of components can be reduced to realize a
low-cost and small-sized device.
Moreover, the memory 38 may be, for example, a storage element with
a trade name "24LC256" manufactured by Microchip Technology Inc.,
US. This storage element has a large capacity in spite of its
compactness, so that the size of the ultraviolet measuring device
10 can be reduced.
The storage content of the memory 38 in the ultraviolet measuring
device 10 is explained in the following.
The memory 38 comprises: a header section which stores various
kinds of information on measurement data (ultraviolet intensities);
a measured data section which stores actually measured data; a
program data section which stores calculation programs; and a
set-value section which stores various kinds of set values. The
program data section and the set value section store various kinds
of calculation programs based on the above-described formulae which
correct actually measured values, and various kinds of set values.
Examples of the set values include sun altitude information, sun
altitude correction factors, standard solar ultraviolet
intensities, UV indices, local ozone concentration information, and
kinds of ultraviolet protective agents corresponding to PFA values
and PA values. Examples of the programs include programs by which
ultraviolet intensities within specific ultraviolet wavelength
ranges (for example, erythema ultraviolet intensities) are
obtained, programs by which amounts of erythema ultraviolet are
obtained, and programs by which UV indices are obtained. Examples
of the formulae used in the programs include the formulae (17),
(18), (20), and (22).
In the embodiment, in order to prevent leakage of the measured data
to the outside, the measured data is stored in the measured data
section after encoded according to a predetermined encoding method.
Information and the like which indicate the above encoding method
are stored in the above-described header section. The encoding
method is not limited to a specific one, but various kinds of
encoding technologies can be appropriately selected as the
method.
Subsequently, the operations of ultraviolet measuring steps in the
ultraviolet measuring device 10 are explained in the following,
referring to FIGS. 3 and 4. Here, FIG. 3 is a flow chart showing
the operation at the ultraviolet measuring steps executed in the
CPU 34. That is, the correction unit, calculating unit, and
deciding unit correspond to the CPU 34.
In the following, as an example, described are the ultraviolet
measuring process comprising determining an erythema ultraviolet
intensity from an actually measured value and obtaining the
erythema ultraviolet amount and UV index from the erythema
ultraviolet intensity. However, the ultraviolet intensity of a
specific wavelength range is not limited to the erythema
ultraviolet intensity, and may be, for example, the ultraviolet
intensity within the UVB range.
At a Step 100 in FIG. 3, ultraviolet is measured with the
ultraviolet sensitive element 18 so as to acquire an actually
measured ultraviolet amount (measured UV value), and the acquired
information (the actually measured value) is stored in an unused
storage area of the data section in the memory 38. Then, the
process proceeds to a Step 102.
At the Step 102, position information (latitude information) is
acquired from the GPS receiver 24; date and time information
(month, day, and time) is acquired from the calendar/clock 36; the
information (actually measured value UV0) acquired in the Step 100
and set values to be used in determining the erythema ultraviolet
intensity are retrieved from the memory 38; the actually measured
value is corrected according to the standard intensity ratio and
the sun altitude correction factor for the erythema ultraviolet
intensity; and the acquired information is stored in an unused
storage area of the measured data section in the memory 38. Then,
the process proceeds to a Step 104.
At the Step 104, the information (erythema ultraviolet intensity)
acquired in Step 102 and set values to be used in obtaining the
erythema ultraviolet amount and the UV index from the information
acquired at the Step 102 are retrieved from the memory 38; the
erythema ultraviolet amount and the UV index are obtained; and the
acquired information is stored in an unused storage area of the
measured data section in the memory 38. Then, the process is
completed.
Moreover, at a Step 200 shown in FIG. 4, the erythema ultraviolet
intensity obtained at the above-described Step 102 is retrieved
from the memory 38. Then, the process proceeds to a Step 202.
At the Step 202, set values (sun altitude information for an
arbitrary point in time) which have been stored in the memory 38
and are to be used in obtaining erythema ultraviolet intensity as
of the arbitrary point in time are retrieved from the memory 38;
the acquired erythema ultraviolet intensity is corrected according
to the sun altitude information for the arbitrary point in time;
the erythema ultraviolet intensity is obtained; and the acquired
information is stored in an unused storage area of the measured
data section in the memory 38. Then, the process proceeds to a Step
204.
At the Step 204, the information (erythema ultraviolet intensity as
of the arbitrary point in time) acquired at the Step 202 and set
values to be used in obtaining the erythema ultraviolet amount and
the UV index from the information acquired at the Step 202 are
retrieved from the memory 38; the erythema ultraviolet amount and
the UV index are obtained; and the acquired information is stored
in an unused storage area of the measured data section in the
memory 38. Then, the process is completed.
Further, though not shown in figures, the following constitution
may be applied: a PFA (Protection factor of UVA) value and a PA
value are obtained from the erythema ultraviolet amount and the
integrated erythema ultraviolet intensity, and the obtained values
are compared with the PFA values and the PA values of the
ultraviolet protective agents which have been stored in the memory
38, to determine a required ultraviolet protective agent.
The information stored in the memory 36 and the acquired
information are displayed on the liquid crystal panel display
16.
The ultraviolet measurement process in the ultraviolet measuring
device 10 explained above are conducted according to the
ultraviolet measuring method of the invention.
This embodiment is also applicable to the method and the device
using the conversion factor. In that case, the conversion formulae
and set values to be used in the conversion are stored in the
memory 38 and the conversion factor is used in the Step 102.
The ultraviolet measuring device 10 according to the embodiment may
be integrated with a portable device (such as a clock, a cellular
telephone, a portable electronic mail apparatus, a portable
navigator, or a portable computer).
In this particular embodiment, the output of the ultraviolet
sensitive element 18 may be a photovoltaic current flowing between
electrodes, or a photoelectric current obtained by applying a
voltage. However, the ultraviolet sensitive element 18 is
preferably of photoelectromotive-current type since the electric
power of the portable device is not consumed.
Further, in the ultraviolet measuring device 10 in this embodiment,
the ultraviolet sensitive element 18 may be disposed on the
backside of the window material provided on the display element of
the portable device, or disposed between the window material and
the display element surface. Furthermore, the ultraviolet sensitive
element 18 may be disposed on a surface of the display element, or
disposed on a location with a separate incidence window.
The position information is acquired with the GPS receiver 24 in
the ultraviolet measuring device 10 according to the embodiment.
However, the acquisition method is not limited to the above
configuration. For example, the following configuration may be
applied: the position information of an arbitrary location is
stored in the memory 38 before the measurement, then a required
piece of position information is retrieved upon specification by a
user. Another example of the configuration utilizes a PHS (Personal
Handy-phone System) in acquiring the position information.
It should be noted that the above-described embodiments should not
be interpreted as limiting the invention to the embodiments.
Therefore, various variations and modifications may be made as long
as the requirements of the present invention are satisfied.
According to the invention, an ultraviolet measuring method and an
ultraviolet measuring device are provided by which specific
ultraviolet information can be obtained at any time from an
actually measured value measured by an ultraviolet sensitive
element with a specific spectral sensitivity in an easy and simple
manner, and by which a total amount of ultraviolet can be measured
at the same time.
Moreover, there are provided an ultraviolet measuring method and an
ultraviolet measuring device by which ultraviolet information for
an arbitrary point in time can be predicted.
* * * * *